Date: Sat, 29 Mar 2025 18:22:53 -0400
From: Bruce Momjian <bruce@momjian.us>
To: "Fujii.Yuki@df.MitsubishiElectric.co.jp"
 <Fujii.Yuki@df.mitsubishielectric.co.jp>
Cc: Tomas Vondra <tomas@vondra.me>, Jelte Fennema-Nio <postgres@jeltef.nl>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>,
	Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>,
	Stephen Frost <sfrost@snowman.net>,
	Andres Freund <andres@anarazel.de>,
	Tomas Vondra <tomas.vondra@enterprisedb.com>,
	Julien Rouhaud <rjuju123@gmail.com>,
	Daniel Gustafsson <daniel@yesql.se>,
	vignesh C <vignesh21@gmail.com>,
	Alexander Pyhalov <a.pyhalov@postgrespro.ru>
Subject: Re: Partial aggregates pushdown
Message-ID: <Z-hyve2DLzBpdDdW@momjian.us>
References: <Zr5vUoXA4sCyZjsX@momjian.us>
 <CAGECzQRFPBsKFk4D56M8yt2TrFdRu_0gDbbBE1887x7LWU_ukg@mail.gmail.com>
 <ZsTJXZq2pcx1Pst-@momjian.us>
 <CAGECzQTx5Ofe8zHXgQHn5cKwaydqHOK8qdWvDyyBPCTnEfvUvw@mail.gmail.com>
 <ZsTjTkUxZ8TnoVWp@momjian.us>
 <91f71f11-3431-49ab-95d0-1c5c90be9fb0@vondra.me>
 <ZsdzvMLLQ-KYoy7J@momjian.us>
 <ea31e84d-609d-47f5-9490-2d1c2551d587@vondra.me>
 <ZseR7c0LgSSmouB6@momjian.us>
 <TYRPR01MB13941CEA16574771B1BFD130595A02@TYRPR01MB13941.jpnprd01.prod.outlook.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: 
 <TYRPR01MB13941CEA16574771B1BFD130595A02@TYRPR01MB13941.jpnprd01.prod.outlook.com>
Archived-At: 
 <https://www.postgresql.org/message-id/Z-hyve2DLzBpdDdW%40momjian.us>
Precedence: bulk

On Fri, Mar 28, 2025 at 02:00:44AM +0000, Fujii.Yuki@df.MitsubishiElectric.co.jp wrote:
> Hi Bruce, Jelte, hackers.
> 
> I apologize for my late response.
> 
> > From: Jelte Fennema-Nio <postgres@jeltef.nl>
> > Sent: Thursday, August 8, 2024 8:49 PM
> > SUMMARY OF THREAD
> > 
> > The design of patch 0001 is agreed upon by everyone on the thread (so far). This adds the PARTIAL_AGGREGATE label for
> > aggregates, which will cause the finalfunc not to run. It also starts using PARTIAL_AGGREGATE for pushdown of
> > aggregates in postgres_fdw. In 0001 PARTIAL_AGGREGATE is only supported for aggregates with a non-internal/pseudo
> > type as the stype.
> > 
> > The design for patch 0002 is still under debate. This would expand on the functionality added by adding support for
> > PARTIAL_AGGREGATE for aggregates with an internal stype. This is done by returning a byte array containing the bytes
> > that the serialfunc of the aggregate returns.
> > 
> > A competing proposal for 0002 is to instead change aggregates to not use an internal stype anymore, and create dedicated
> > types. The main downside here is that infunc and outfunc would need to be added for text serialization, in addition to the
> > binary serialization. An open question is: Can we change the requirements for CREATE TYPE, so that types can be created
> > without infunc and outfunc.
> 
> I rebased the patch 0001 and add the documentation to it.

Okay, this is too late for PG 18 but I am hopeful we can make progress
on this for PG 19.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Do not let urgent matters crowd out time for investment in the future.